This invention relates generally to a fluid system for supplying a low pressure fluid and a high pressure fluid and, more particularly, to a fluid system providing alternative conditional flow paths for supplying the high pressure fluid.
In the past, fluid systems in engines have been called upon to both lubricate and cool the engines. Nowadays, fluid systems in engines may be called up to perform several different functions, not only including the traditional functions of lubricating and cooling the engine, but also to provide fluid to actuate other components. These different functions may require fluid to be supplied at different pressures, and thus, present day systems may be called upon to supply both a low pressure fluid to a low pressure accumulator and a high pressure fluid to a high pressure accumulator. The low pressure accumulator may then supply the fluid for lubricating and cooling the engine and engine components, for instance, to a gallery of cooling passages, bearing areas, rocker arms, etc., while the high pressure accumulator may supply a working fluid, for instance, to actuate steering, lifting, and/or compression release braking cylinders. Such a fluid accumulator may include, for instance, a rail, a manifold, a gallery of passages, a filter system, a cooler system, a pumping system, or any other component or system that provides a volume wherein fluid may accumulate.
One application for a dual pressure fluid system may be to supply a fluid, for instance, a lube oil, at a low pressure to lubricate and cool the engine and to also supply this fluid at a high pressure to actuate, or assist in the actuation of, fuel injectors. However, prior to starting the engine, and particularly prior to cold starts, drainage in the fluid system may have allowed the standing pressures within the system to dissipate, or at least partially dissipate, and the quantity of fluid retained in the normally pressurized volumes to be reduced, for instance, by standing fluids draining back to a sump. Thus, upon start-up of the engine when the low pressure lubrication or cooling pump in the fluid pressure system is activated, there may be a delay or lag time in filling and pressurizing the inlet side of the high pressure pump or pump section. This delay may be aggravated if the fluid pumped from the lubrication or cooling pump first refills and repressurizes the low pressure fluid accumulator, for instance, a manifold and associated passages, which typically encompass a fairly large volume. This delay may be especially aggravated if some of the fluid in the low pressure portion of the system, for instance, fluid in a filter system and/or a cooling system, has drained through the other engine components, such as piston cooling jets and bearings, after the previous hot shut down. In this application, any delay in pressurizing the inlet side of the high pressure pump translates into a delay in actuating the fuel injectors and a corresponding delay in starting the engine.
U.S. Pat. No. 5,121,730 issued to Ausman et al., dated Jun. 16, 1992, discloses the use of two paths to bypass a fluid filter in a hydraulic actuating fluid circuit. The first path bypasses the fluid filter when the pressure differential between the outlet of a first pump and a priming reservoir is great enough to cause a check valve in this first path to open. The second path bypasses the fluid filter in the hydraulic actuating fluid circuit when the difference between the pressures upstream and downstream of the fluid filter (for example, when the filter is plugged with debris) causes a bypass valve to open.
There is a need in the engine industry, particularly with respect to engines using a dual pressure fluid system for, among other things, actuating fuel injectors, for a dual pressure fluid system that efficiently and quickly supplies fluid to the high pressure portion of the system upon start-up. The present invention is directed to overcoming one or more of the problems or disadvantages associated with the prior art.
In one aspect of the invention, a fluid system for supplying a low pressure fluid and a high pressure fluid is provided. The fluid system may include first and second fluid pumps, a fluid filter, low and high pressure fluid accumulators, and a priority valve. The first fluid pump is configured to discharge a first fluid pump outlet flow, which is divisible into first and second portions. The fluid filter is connected to the first fluid pump to receive the first portion of the first fluid pump outlet flow and is configured to discharge a fluid filter outlet flow, which is divisible into first and second portions. The low pressure fluid accumulator is connected to the fluid filter to receive the first portion of the fluid filter outlet flow. The priority valve is connected to the first fluid pump to receive the second portion of the first fluid pump outlet flow and to the fluid filter to receive the second portion of the fluid filter outlet flow, and is configured to discharge a priority valve outlet flow. The priority valve is movable between a first position, which provides a first priority valve fluid flow path between the second portion of the first fluid pump outlet flow and the priority valve outlet flow, and a second position, which provides a second priority valve fluid flow path between the second portion of the fluid filter outlet flow and the priority valve outlet flow. The second fluid pump is connected to the priority valve to receive the priority valve outlet flow and is configured to discharge a second fluid pump outlet flow. The high pressure fluid accumulator is connected to the second fluid pump to receive the second fluid pump outlet flow.
In another aspect of the invention, a pressure and temperature controlled valve for controlling the flow path of a fluid is provided. The valve may include a housing, a spool, a resilient element, and a thermally reactive element. The housing has a first fluid inlet port, a second fluid inlet port, and a fluid outlet port. The spool is located within the housing and is movable between a first position, at which flow of the fluid along a first flow path between the first fluid inlet port and the fluid outlet port is passed and flow of the fluid along a second flow path between the second fluid inlet port and the fluid outlet port is blocked, and a second position, at which flow of the fluid along the first flow path is blocked and flow of the fluid along the second flow path is passed. The resilient element biased the spool relative to the housing to a first position. The thermally reactive element is exposed to a temperature input, the thermally reactive element having a first configuration in response to the temperature input being at a first temperature, the first configuration allowing the spool to be in the first position, and having a second configuration in response to the temperature input being at a second temperature, the second configuration preventing the spool from being in the first position.
In a further aspect of the invention, a method for supplying a low pressure fluid and a high pressure fluid is provided. The method may include pumping a fluid through a first fluid pump to create a first pumped flow and filtering a first portion of the first pumped flow to create a filtered flow. The method may further include passing a first portion of the filtered flow to a first inlet port of a priority valve and passing a second portion of the first pumped flow to a second inlet port of a priority valve. The method may also include transmitting one of the first portion of the filtered flow and the second portion of the first pumped flow through the priority valve to create a priority valve outlet flow, passing the priority valve outlet flow to a second fluid pump, and pumping the priority valve outlet flow through the second fluid pump to create a second pump outlet flow.
It is to be understood that both the foregoing general background, the following detailed description, and the drawings are exemplary and explanatory only and are not restrictive of the invention.